Hologram duplicating device and method

ABSTRACT

A hologram duplicating apparatus ( 10 ) includes a first optical system ( 30 ) for carrying out exposure recording of holographic stereogram image on a recording medium for hologram to produce an original H 1 , a second optical system ( 60 ) for carrying out exposure recording of image recorded on the original H 1  on a recording medium for hologram disposed at a predetermined distance from the original H 1  by using diffracted light obtained by illuminating the original H 1  to produce intermediate hologram H 2 , and a third optical system ( 70 ) for carrying out exposure recording of image recorded on the intermediate hologram H 2  on a recording medium for hologram disposed at a predetermined distance from the intermediate hologram H 2  by using diffracted light obtained by illuminating the intermediate hologram H 2  to produce edge lit hologram H 3 .

BACKGROUND OF THE INVENTION

This invention relates to a hologram duplicating apparatus and ahologram duplicating method for duplicating hologram in which aholographic stereogram is used as the original, a hologram producingapparatus and a hologram producing method for producing hologram inwhich a holographic stereogram is used as the original, and anintermediate hologram producing apparatus and an intermediate hologramproducing method for producing intermediate hologram used forduplication or production thereof.

Holographic stereograms are produced by allowing a large number ofimages obtained by successively imaging object from differentobservation points to be original image to successively expose andrecord such images as rectangular or dot-shaped element holograms on asingle recording medium for hologram. In the case where this holographicstereogram is observed by an eye from a certain position,two-dimensional image which is a set of image information of a portionof respective element holograms is recognized, and in the case wherethis holographic stereogram is observed at another position horizontallyshifted from this position, two-dimensional image which is a set ofimage information of another portion of respective element holograms isrecognized. Accordingly, in the holographic stereogram, in the casewhere user observes this holographic stereogram by both eyes, exposedrecording image is recognized as three-dimensional image by parallax ofleft and right eyes.

The above-described holographic stereogram is produced by a holographicstereogram producing apparatus 100 generally shown in FIG. 1A. Theholographic stereogram producing apparatus 100 is constituted by a laserlight source 101 for emitting coherent laser beam L10 of singlewavelength, a half mirror 102 for dividing the emitted laser beam L10into object light L11 and reference light L12, optical components 103 to107 and an indicator 108 which constitute optical system of the objectlight L11, optical components 109 to 11 which constitute optical systemof the reference light L12, and an electrically operated stage 113 forholding a recording medium 112 for hologram onto which object light L11and reference light L12 are converged, and caused to undergo travelingdrive.

Specifically, the optical system of object light L11 consists of areflection mirror 103, a first cylindrical lens 104 for magnifyingobject light L11 in one-dimensional direction, a collimator lens 105 forchanging the magnified object light L11 into parallel light, aprojection lens 106, and a second cylindrical lens 107 for conductingobject light L11 to the hologram recording medium 112 of an exposurerecording unit P100 which are respectively arranged from the input sidethereof along the optical axis. The indicator 108 is constituted byliquid crystal panel of the transmission type, and is disposed betweenthe collimator lens 105 and the projection lens 106. On the indicator108, image based on image data outputted from image processing unit (notshown) is displayed.

Specifically, the optical system of the reference light L12 consists ofa cylindrical lens 109 for magnifying reference light L12 inone-dimensional direction, a collimator lens 110 for changing themagnified reference light L12 into parallel light, and a reflectionmirror 111 for reflecting the reference light L12 to conduct it into thehologram recording medium 112 which are respectively arranged from theinput side thereof along the optical axis.

The hologram recording medium 112 is constituted by, e.g.,photosensitive film, and is held by the electrically operated stage 113as shown in FIG. 1B. When this electrically operated stage 113 isdriven, the hologram recording medium 112 is caused to intermittentlyundergo traveling drive in the direction indicated by the arrow b in thefigure.

As shown in FIG. 1A, laser beam L10 is emitted from the laser lightsource 101 and is incident on the half mirror 102. Thus, the laser beamis divided into object light L11 and reference light L12 by this halfmirror 102.

The object light L11 is incident on the indicator 108 through thecylindrical lens 104 and the collimator lens 105, and is caused toundergo image modulation in accordance with element image displayed whenthe object light L11 is transmitted through this indicator 108. Theimage-modulated object light L11 is incident on the hologram recordingmedium 112 positioned at the exposure recording unit P100 through theprojection lens 106 and the cylindrical lens 107. Moreover, thereference light L12 is incident on the hologram recording medium 112positioned at the exposure recording unit P100 through the opticalsystem of the cylindrical lens 109, the collimator lens 110 and thereflection mirror 111.

Accordingly, interference fringes produced by interference of the objectlight L11 which has been image-modulated by image displayed on theindicator 108 and reference light L12 are successively exposed andrecorded in rectangular or dot form as element holograms on the hologramrecording medium 112. In this way, holographic stereogram is produced.

Meanwhile, in ordinary hologram, illumination light source forreproducing three-dimensional image and hologram are spatiallyseparated. For this reason, ordinarily, broad space is required forreproduction, and the positional relationship between hologram and theillumination light source must be set to the determined condition inorder to carry out reproduction in the optimum condition. This issimilar also in the holographic stereogram consisting of plural elementholograms.

On the contrary, if the illumination light source and hologram areintegrated, space for illumination becomes unnecessary so thatminiaturization can be realized. In addition, since the positionalrelationship between hologram and the illumination light source isconstant at all times, reproduction can be carried out always in optimumcondition. Further, as a hologram which realizes this, there is hologramof the so-called edge lit type which allows a recording medium to be incontact with all optically transparent light introduction block to carryout recording and/or reproduction.

When a transmission type edge lit hologram in which three-dimensionalimage is reproduced by light transmitted through a recording medium isproduced, a recording medium 121 for hologram is attached to one surface120 a of a light introduction block 120 consisting of transparentmaterial such as glass or plastic, etc. of suitable thickness as shownin FIG. 2. At this time, ordinarily, the hologram recording medium 121is attached to the light introduction block 120 through index matchingliquid (not shown) in order to prevent total reflection of light.Further, object light 124 from object 123 is irradiated toward thehologram recording medium 121 from the other surface 120 b of the lightintroduction block 120, and reference light 125 is irradiated toward thehologram recording medium 121 from end surface 120 c of the lightintroduction block 120. Thus, the transmission type edge lit hologram isproduced.

Further, when the transmission type edge lit hologram produced in thisway is reproduced, light introduction block such as glass, etc. wasattached to the hologram recording medium to allow illumination light tobe incident from the end surface of that light introduction block tothereby carry out reproduction of hologram. Specifically, as shown inFIG. 3, a hologram 131 is attached to one surface 130 a of a lightintroduction block 130 through index matching liquid (not shown)thereafter to irradiate illumination light 133 for reproduction towardthe hologram 131 from end surface 130 b of the light introduction block130. At this time, light transmitted through the hologram 131 isdiffracted by the hologram 131. Further, reproduction image 135 takesplace by this diffracted light 134. Thus, the reproduction image 135 isobserved by an observer 136.

In the above-mentioned FIG. 3, the case where incident angle ofreproduction illumination light of hologram is 60 degrees was indicatedas an example. By introducing reproduction illumination light 133through the light introduction block 130 in this way, it is possible toprevent surface reflection between hologram recording material and air.Since this effect becomes conspicuous particularly according as lightincident angle of reproduction illumination light 133 becomes sharp, itis considered that the edge lit hologram is advantageous in realizationof compact reproducing unit.

Meanwhile, since the edge lit hologram has various merits as previouslydescribed, there is high possibility that the edge lit hologram isutilized as a general image display apparatus. In this case, it isassumed that the necessity of duplicating a large number of holograms inwhich the same image information is recorded in the state where imagequality is maintained takes place.

Hitherto, in the case of mass-producing duplications of holograms, theso-called one step method in which an original and photosensitivematerial for printing duplication are exposed in the state where theyare caused to be in contact with each other was used as a generaltechnique.

As one example of the one step method, the example where image of theoriginal is duplicated and recorded on other recording medium forhologram in which a holographic stereogram is used as the original toproduce edge lit hologram is shown in FIG. 4.

As shown in FIG. 4, in carrying out duplication and recording, arecording medium 141 for hologram for duplicating and recording image ofthe original is first attached to one surface 140 a of a lightintroduction block 140. Then, an original 142 is attached to thehologram recording medium 141 attached on one surface 140 a of the lightintroduction block 140 through index matching liquid.

In the state where the original is attached in this way, reference light143 equivalent to illumination light for reproduction of the original142 is caused to be incident into this light introduction block 140 fromend surface 140 b of the light introduction block 140.

The reference light 143 incident into the light introduction block 140is transmitted through the hologram recording medium 141 and is incidenton the original 142. The incident light is totally reflected by basefilm (not shown) of the original 142. Further, because of that thereference light 143 totally reflected by the base film is irradiatedonto hologram recording material of the original 142, image recorded onthis hologram recording material is reproduced.

Reproduction light of this original 142 is incident for a second time onthe hologram recording material of the hologram recording medium 141 asobject light. Further, the reproduction light of the original 142incident as object light on the hologram recording material of thishologram recording medium 141 interferes with the reference light 143incident into the light introduction block 140 within this hologramrecording material. Thus, interference fringes of the reproduction lightof the original 142 and the reference light 143 are recorded on thehologram recording material of the hologram recording medium 141, andimage recorded on the original 142 is duplicated and recorded on thehologram recording medium.

In a manner as described above, by the 1 step method, image of theoriginal is duplicated and recorded on other hologram recording mediumin which the holographic stereogram is used as the original. Thus, edgelit hologram is produced.

However, the above-described 1 step method is suitable for duplicationof hologram of the reflection type, but was not suitable for duplicationof hologram in which image quality is maintained because there takeplace many factors which disturb image quality including doublerefraction at the surface of the contact portion of the lightintroduction block and the hologram recording material at the type wherereproduction is carried out in the state in contact with the lightintroduction block like edge lit hologram.

As stated above, there also exist drawbacks in the 1 step methodgenerally used. It can be said the technology for duplicating a largenumber of holograms using a holographic stereogram as the original isnot yet established.

SUMMARY OF THE INVENTION

This invention has been proposed in view of such actual circumstances ofprior arts, and an object of this invention is to provide a hologramduplicating apparatus and a hologram duplicating method for duplicatinghologram in which a reflection type holographic stereogram is used asthe original. Moreover, it is desired to provide a hologram producingapparatus and a hologram producing method for producing edge lithologram without using the above-desired 1 step method. Further, it isdesired to provide an intermediate hologram producing apparatus and anintermediate hologram producing method for producing intermediatehologram used for duplication or production of such hologram or edge lithologram.

In order to attain the above-described objects, a hologram duplicatingapparatus according to this invention is directed to a hologramduplicating apparatus for duplicating hologram in which a holographicstereogram is used as an original, and includes: a first optical systemfor allowing a first object light, which has been image-modulated on thebasis of respective element images of parallax image sequence to beincident on one surface of a first hologram recording medium withoutdiffusion, and for allowing a first reference light having coherencewith the first object light to be incident on the other surface of thefirst hologram recording medium so as to successively carry out exposurerecording of interference fringes produced by the first object light andthe first reference light on the first hologram recording medium aselement holograms, thereby producing the original; a second opticalsystem for allowing a diffracted light obtained by irradiating a firstreproduction light for reproducing image recorded on the originalproduced by the first optical system onto the original to be incident,as a second object light, on one surface of a second hologram recordingmedium disposed with a predetermined distance from the original, and forallowing a second reference light having coherence with the secondobject light to be incident on the other surface of the second hologramrecording medium to carry out exposure recording of interference fringesproduced by the second object light and the second reference light onthe second hologram recording medium as hologram, thereby producing anintermediate hologram; and a third optical system in which anone-dimensional diffusion plate for diffusing incident light inone-dimensional direction is disposed at one surface of a third hologramrecording medium disposed with a predetermined distance from theintermediate hologram produced by the second optical system in such amanner that the principal surface of the one-dimensional diffusion plateis in contact therewith, and for allowing a diffracted light obtained byirradiating a second reproduction light for reproducing image recordedon the intermediate hologram onto the intermediate hologram to beincident on one surface of a third hologram recording medium as a thirdobject light through the one-dimensional diffusion plate and forallowing a third reference light having coherence with the third objectlight to be incident on the other surface of the third hologramrecording medium to carry out exposure recording of interference fringesproduced by the third object light and the third reference light on thethird hologram recording medium as holograms, thereby producing aduplicated hologram.

Thus, hologram is duplicated using the holographic stereogram as theoriginal.

Here, light introduction block consisting of transparent opticalmaterial may be attached on the surface of the third hologram recordingmedium where the third reference light is incident.

Thus, edge lit hologram is produced at the third optical system in thehologram duplicating apparatus.

Moreover, in order to attain the above-described objects, a hologramduplicating method according to this invention is directed to a hologramduplicating method of duplicating hologram in which a holographicstereogram is used as an original, and includes: a first exposure stepof allowing a first object light, which has been image-modulated on thebasis of respective element images of parallax image sequence to beincident on one surface of a first hologram recording medium withoutdiffusion, and of allowing a first reference light having coherence withthe first object light to be incident on the other surface of the firsthologram recording medium so as to successively carry out exposurerecording of interference fringes produced by the first object light andthe first reference light on the first hologram recording medium aselement holograms, thereby producing an original; a second exposure stepof allowing a diffracted light obtained by irradiating a firstreproduction light for reproducing image recorded on the originalproduced at the first exposure step onto the original to be incident, asa second object light, on one surface of a second hologram recordingmedium disposed with a predetermined distance from the original, and ofallowing a second reference light having coherence with the secondobject light to be incident on the other surface of the second hologramrecording medium to carry out exposure recording of interference fringesproduced by the second object light and the second reference light onthe second hologram recording medium as hologram, thereby producing anintermediate hologram; and a third exposure step in which anone-dimensional diffusion plate for diffusing incident light inone-dimensional direction is disposed at one surface of a third hologramrecording medium disposed with a predetermined distance from theintermediate hologram produced at the second exposure step in such amanner that the principal surface of the one-dimensional diffusion plateis in contact therewith, the third exposure step of allowing adiffracted light obtained by irradiating a second reproduction light forreproducing image recorded on the intermediate hologram onto theintermediate hologram to be incident on one surface of the thirdhologram recording medium as a third object light through theone-dimensional diffusion plate, and of allowing a third reference lighthaving coherence with the third object light to be incident on the othersurface of the third hologram recording medium to carry out exposurerecording of interference fringes produced by the third object light andthe third reference light on the third hologram recording medium asholograms, thereby producing a duplicated hologram.

Thus, hologram is duplicated using holographic stereogram as theoriginal.

Here, light introduction block consisting of transparent opticalmaterial may be attached to the surface where third reference light isincident in the third hologram recording medium.

Thus, edge lit hologram is produced at the third exposure step in thehologram duplicating method.

Further, a hologram producing apparatus according to this invention isdirected to a hologram producing apparatus for producing hologram usingan original holographic stereogram having the configuration in whichplural element holograms are successively arranged along parallaxdirection, and includes intermediate hologram producing means forreproducing image of the original to carry out exposure recording of thereproduced image on a first hologram recording medium to thereby produceintermediate hologram, and hologram producing means for reproducingimage of the intermediate hologram to carry out exposure recording ofthe reproduced image on a second hologram recording medium to therebyproduce hologram, wherein the hologram producing means includes, at thesurface of the second hologram recording medium, diffusing means fordiffusing image reproduced from the intermediate hologram in a directioncorresponding to a direction perpendicular to the parallax direction atthe surface of the original.

Here, the intermediate hologram producing means and the hologramproducing means may share a reproduction optical system for reproducingimage and an exposure recording optical system for carrying out exposurerecording of reproduced image.

Further, a hologram producing apparatus according to this invention isdirected to a hologram producing apparatus for reproducing image usingan original holographic stereogram having the configuration in whichplural element holograms are successively arranged along parallaxdirection to produce hologram by using intermediate hologram produced bycarrying out exposure recording of the reproduced image on a firsthologram recording medium, and includes hologram producing means forreproducing image of the intermediate hologram to carry out exposurerecording of the reproduced image on a second hologram recording mediumto thereby produce hologram, wherein the hologram producing meansincludes, at the surface of the second hologram recording medium,diffusing means for diffusing image reproduced from the intermediatehologram in a direction corresponding to a direction perpendicular tothe parallax direction at the surface of the original.

Further, a hologram producing apparatus according to this invention isdirected to a hologram producing apparatus for reproducing image usingan original holographic stereogram having the configuration in whichplural element holograms are successively arranged along parallaxdirection to produce hologram by using intermediate hologram produced bycarrying out exposure recording of the reproduced image on a firsthologram recording medium, and includes hologram producing means forreproducing image of the intermediate hologram to carry out exposurerecording of the reproduced image on a second hologram recording medium,wherein hologram produced by the hologram producing means is such thatangle of visibility in a direction corresponding to a directionperpendicular to the parallax direction at the surface of the originalis greater than angle of visibility of holographic stereogram of theoriginal.

Here, these holograms produced at the hologram producing apparatus are,e.g., edge lit hologram.

Thus, it is possible to produce hologram, particularly edge litholograms using a holographic stereogram as the original.

Further, a hologram producing method according to this invention isdirected to a hologram producing method of producing hologram using anoriginal holographic stereogram having the configuration in which pluralelement holograms are successively arranged in a parallax direction, andincludes an intermediate hologram producing step of reproducing image ofthe original to carry out exposure recording of the reproduced image ona first hologram recording medium to thereby produce intermediatehologram, and a hologram producing step of reproducing image of theintermediate hologram to carry out exposure recording of the reproducedimage on a second hologram recording medium to thereby produce hologram,wherein, at the hologram producing step, image reproduced from theintermediate hologram is diffused in a direction corresponding to adirection perpendicular to the parallax direction at the surface of theoriginal by diffusing means disposed at the surface of the secondhologram recording medium.

Here, at the intermediate hologram producing step and the hologramproducing step, a reproduction optical system for reproducing image andan exposure recording optical system for carrying out exposure recordingof the reproduced image may be shared.

Further, a hologram producing method according to this invention isdirected to a hologram producing method of reproducing image using anoriginal holographic stereogram having the configuration in which pluralelement holograms are successively arranged along parallax direction toproduce hologram by using intermediate hologram produced by carrying outexposure recording of the reproduced image on a first hologram recordingmedium, and includes a hologram producing step of reproducing image ofthe intermediate hologram to carry out exposure recording of thereproduced image on a second hologram recording medium to therebyproduce hologram, wherein, at the hologram producing step, imagereproduced from the intermediate hologram is diffused in a directioncorresponding to a direction perpendicular to the parallax direction atthe surface of the original plate by diffusing means disposed at thesurface of the second hologram recording medium.

Further, a hologram producing method according to this invention isdirected to a hologram producing method of reproducing image using anoriginal holographic stereogram having the configuration in which pluralelement holograms are successively arranged along parallax direction toproduce hologram by using intermediate hologram produced by carrying outexposure recording of the reproduced image on a first hologram recordingmedium, and includes a hologram producing step of reproducing image ofthe intermediate hologram to carry out exposure recording of thereproduced image on a second hologram recording medium, wherein hologramproduced at the hologram producing step is such that angle of visibilityin a direction corresponding to a direction perpendicular to theparallax direction at the surface of the original is greater than angleof visibility of holographic stereogram of the original.

Here, these holograms produced by the hologram producing method are,e.g., edge lit hologram.

Thus, it is possible to produce hologram, particularly edge lit hologramusing a holographic stereogram as the original.

Further, an intermediate hologram producing apparatus according to thisinvention is directed to an intermediate hologram producing apparatusfor producing intermediate hologram used for producing hologram using anoriginal holographic stereogram having the configuration in which pluralelement holograms are successively arranged along parallax direction,and includes intermediate hologram producing means for reproducing imageof the original to carry out exposure recording of the reproduced imageon a recording medium for hologram to thereby produce the intermediatehologram, wherein intermediate hologram produced by the intermediatehologram producing means is such that angle of visibility in a directioncorresponding to a direction perpendicular to the parallax direction atthe surface of the original is substantially the same as angle ofvisibility of holographic stereogram of the original.

Thus, intermediate hologram used when hologram, particularly edge lithologram is produced using a holographic stereogram as the original isproduced.

In addition, in order to attain the above-described objects, anintermediate hologram producing method according to this invention isdirected to an intermediate hologram producing method of producingintermediate hologram used for producing hologram using an originalholographic stereogram having the configuration in which plural elementholograms are successively arranged along parallax direction, andincludes an intermediate hologram producing step of reproducing image ofthe original to carry out exposure recording of the reproduced image ona recording medium for hologram, wherein intermediate hologram producedat the intermediate hologram producing step is such that angle ofvisibility in a direction corresponding to a direction perpendicular tothe parallax direction at the surface of the original is substantiallythe same as angle of visibility of holographic stereogram of theoriginal.

Thus, intermediate hologram used when hologram, particularly edge lithologram is produced using a holographic stereogram as the original isproduced.

Still further objects of this invention and more practical meritsobtained by this invention will become more apparent from thedescription of the embodiment which will be given below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a front view showing optical system of a conventionalholographic stereogram producing apparatus, and FIG. 1B is a plan viewthereof.

FIG. 2 is a view for explaining a conventional method of producingtransmission type edge lit hologram.

FIG. 3 is a view for explaining a conventional method of reproducingtransmission type edge lit hologram.

FIG. 4 is a view for explaining the principle of a conventionalduplicating method for edge lit hologram by duplication recording of 1step method.

FIG. 5 is a block diagram for explaining outline of a hologramduplicating apparatus in this embodiment.

FIG. 6 is an essential part cross sectional view for explainingrecording medium for hologram used in the hologram duplicatingapparatus.

FIG. 7A is a view showing initial state of photosensitive process of thehologram recording medium, FIG. 7B is a view showing exposure state, andFIG. 7C is a view showing fixing state.

FIG. 8 is a view for explaining the configuration of the entirety of thehologram duplicating apparatus.

FIG. 9A is a front view showing a first optical system that holographicstereogram producing unit in the hologram duplicating apparatus has, andFIG. 9B is a plan view thereof.

FIG. 10 is a view for explaining processing at a second optical systemthat hologram duplicating unit in the hologram duplicating apparatushas.

FIG. 11 is a view for explaining front view of the second opticalsystem.

FIG. 12 is a view for explaining processing at a third optical systemthat the hologram duplicating unit has.

FIG. 13 is a view for explaining front view of the third optical system.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

More practical embodiment to which this invention is applied now will bedescribed in detail with reference to the attached drawings.

As shown in FIG. 5, this embodiment is directed to a hologramduplicating apparatus at least including a holographic stereogramproducing unit 20 including a first optical system 30, and a hologramduplicating unit 50 including a second optical system 60 and a thirdoptical system 70. At the holographic stereogram producing unit 20,interference fringes are successively exposed and recorded, e.g., inrectangular form as element holograms on a recording medium for hologramconsisting of elongated photosensitive film to produce holographicstereogram serving as an original to produce the so-called edge lithologram at the hologram duplicating unit 50 on the basis of thisoriginal.

Although described later, processing at the third optical system 70 isrepeated, thereby making it possible to duplicate an arbitrary number ofedge lit holograms.

First, prior to description of respective components, exposure recordingprinciple on the hologram recording medium will be described.

As shown in FIG. 6, a hologram recording medium 3 is the so-called filmcoating type recording medium in which a photo-polymer layer 5consisting of photo-polymerization type photo-polymer is formed on afilm base material 4, and a cover sheet layer 6 is adherently formed onthis photo-polymer layer 5.

As shown in FIG. 7A, in such hologram recording medium 3,photo-polymerization type photo-polymer constituting the photo-polymerlayer 5 is in the state where monomers M are uniformly diffused withinmatrix polymer in the initial state. Because of that laser beams LAhaving power of 10 mJ/cm² to 400 mJ/cm² are irradiated ontophoto-polymerization type photo-polymer, monomers M which have beenuniformly dispersed within matrix polymer at the exposure portion arepolymerized as shown in FIG. 7B so that there results polymerizationstate.

In the photo-polymerization photo-polymer, according as polymerizationis advanced, because of unevenness of concentration of monomer Mresulting from the fact that monomers M are moved from the periphery,there take place modulations of refractive index at the exposed portionand the non-exposed portion. Thereafter, in the photo-polymerizationtype photo-polymer, as shown in FIG. 7C, because of that ultraviolet rayor visible light LB having power of about 1000 mJ/cm² is irradiated ontothe entire surface, polymerization of monomers M is completed withinmatrix polymer. In the hologram recording medium 3, because refractiveindex of the photo-polymerization type photo-polymer constituting thephoto-polymer layer 5 as stated above changes in accordance withincident laser beam LA, interference fringes produced by interferencebetween object light and reference light are caused to undergo exposurerecording as change of refractive index.

The hologram duplicating apparatus uses the film coating type recordingmedium in which photo-polymer layer 5 is constituted by suchphoto-polymerization type photo-polymer as the hologram recording medium3, whereby a step of implementing special development processing to thehologram recording medium 3 after exposure at the first optical system30, the second optical system 60 and the third optical system 70 becomesunnecessary. Accordingly, the hologram duplicating apparatus cansimplify its configuration because developing unit, etc. becomesunnecessary, and can quickly produce holographic stereogram. Thus, it ispossible to quickly produce holograms using the holographic stereogramas the original.

Then, the overall configuration of the hologram duplicating apparatuswill be described. The hologram duplicating apparatus carries outexposure recording of holographic stereogram image on theabove-described hologram recording medium 3 to duplicate holograms usingthe holographic stereogram image as the original.

As shown in FIG. 8, the hologram duplicating apparatus 10 includes aimage data processing unit 11 for carrying out processing of image datasubject to exposure recording, a control unit 12 including a computer 13for control for generally controlling this hologram duplicatingapparatus 10, holographic stereogram producing unit 20 for producingholographic stereogram serving as an original H₁, and hologramduplicating unit 50 for duplicating hologram on the basis of holographicstereogram serving as the original H₁ produced at the holographicstereogram producing unit 20.

The image data processing unit 11 includes a computer 16 for imageprocessing and a memory unit 17, and generates parallax image datasequence D3 on the basis of image data, such as, for example, imagingimage data D1 including parallax information provided from a parallaximage sequence imaging unit 1 including multiple-lens camera or movablecamera, etc., or computer image data D2 including parallax informationgenerated by a computer 2 for image data generation, etc.

It is to be noted that the imaging image data D1 is, e.g., plural imagedata obtained by simultaneous photographing by multiple-lens camera orcontinuous photographing by movable camera, and parallax information isincluded between respective image data constituting the imaging imagedata D1. In addition, computer image data D2 is, e.g., plural image dataprepared as CAD (Computer Aided Design) or CG (Computer Graphics), andparallax information is included between respective image dataconstituting the computer image data D2.

The image data processing unit 11 implements a predetermined imageprocessing for holographic stereogram to generate parallax image datasequence D3 based on these imaging image data D1 and/or computer imagedata D2 by the image processing computer 16 to generate hologram imagedata D4. The hologram image data D4 is temporarily stored with respectto the memory unit 17, e.g., memory or hard disc unit, etc. As describedlater, the image data processing unit 11 successively reads out elementhologram image data D5 every one image from hologram image data D4stored in the memory unit 17 when element hologram image is caused toundergo exposure recording on recording medium h₁ for hologram toprovide these element hologram image data D5 to the control computer 13in the control unit 12. Here, the hologram recording medium h₁ is mediumwhich has the same quality as the previously described hologramrecording medium 3, and is medium in which the hologram recording medium3 is caused to be elongated.

The control computer 13 controls the holographic stereogram producingunit 20 to successively carry out exposure recording of element displayimages based on element hologram image data D5 provided from the imagedata processing unit 11 as rectangular element hologram on the hologramrecording medium h₁ set at a portion of the holographic stereogramproducing unit 20. In this instance, the control computer 13 controlsoperations of respective mechanisms of the holographic stereogramproducing unit 20 and the hologram duplicating unit 50 as describedlater.

The holographic stereogram producing unit 20 includes the first opticalsystem 30, and produces holographic stereogram serving as the originalH₁ under control by the control computer 13.

The hologram duplicating unit 50 includes the second optical system 60and the third optical system 70, and duplicates edge lit hologram H₃ byprocessing as described below using holographic stereogram produced atthe holographic stereogram producing unit 20 as the original H₁.

The first optical system 30, the second optical system 60 and the thirdoptical system 70 will be described below specifically in order.

The first optical system 30 includes, as shown in FIGS. 9A and 9B, anincident optical system 30A, an object optical system 30B and areference optical system 30C. Among them, the object optical system 30Band the reference optical system 30C are constituted so that respectiveoptical path lengths until exposure recording unit P1 of object light L2and reference light L3 are caused to be substantially the same in orderto enhance coherence of object light L2 and reference light L3. In thisexample, in the hologram duplicating apparatus 10, since recordingmedium h₁ for hologram serving as photosensitive material is used, thecasing of the apparatus (not shown) including the first optical system30, the second optical system 60 and the third optical system 70 has thestructure in which light-shielding property of at least these opticalsystems is held.

The incident optical system 30A includes a laser light source 31 foremitting laser beam L1, a shutter mechanism 32 for allowing this laserbeam L1 to be incident on the succeeding stage or cutting off it, and ahalf mirror 33 for dividing the laser beam L1 into object light L2 andreference light L3.

The laser light source 31 is a laser unit such as semiconductorexcitation YAG laser unit, water-cooled argon ion laser unit orwater-cooled krypton laser unit which emits coherent laser beam L1 ofsingle wavelength, etc.

The shutter mechanism 32 is caused to undergo opening/closing operationby control signal C1 outputted from the control computer 13 incorrespondence with output timing of element hologram image data D5 toallow laser beam L1 to be incident on hologram recording medium h₁positioned at the exposure recording unit P1 through the optical systemof the succeeding stage, or to cut off incidence on the hologramrecording medium h₁ of laser beam L1.

The half mirror 33 divides incident laser beam L1 into transmitted lightand reflected light. With respect to the laser beam L1, the transmittedlight is used as the above-described object light L2, whereas thereflected light is used as reference light L3. These object light L2 andreference light L3 are respectively incident on the object opticalsystem 30B and the reference optical system 30C provided at succeedingstages.

The object optical system 30B has the configuration in which opticalparts such as a reflection mirror 34, a first cylindrical lens 35, acollimator lens 36, a projection lens 37 and a second cylindrical lens38, etc. are arranged in order from the input side thereof along theoptical axis.

The reflection mirror 34 totally reflects object light L2 transmittedthrough the half mirror 33. Object light L2 totally reflected by thisreflection mirror 34 is provided to the first cylindrical lens 35.

The first cylindrical lens 35 has the configuration in which convex lensand pin hole are combined, and magnifies object light L2 totallyreflected by the reflection mirror 34 in one-dimensional direction incorrespondence with display surface width of transmission type liquidcrystal indicator 39 which will be described later.

The collimator lens 36 changes the object light L2 magnified by thefirst cylindrical lens 35 into parallel light to conduct it to thetransmission type liquid crystal indicator 39.

The projection lens 37 proejcts object light L2 onto the secondcylindrical lens 38.

The second cylindrical lens 38 converges the object light L2 changedinto parallel light with respect to lateral direction at the exposurerecording unit P1.

Moreover, at the object optical system 30B, the transmission type liquidcrystal indicator 39 is disposed in the state positioned between thecollimator lens 36 and the projection lens 37. On the transmission typeliquid crystal indicator 39, element hologram images are successivelydisplayed on the basis of element hologram image data DS provided fromthe control computer 13. In this example, the control computer 13provides control signal C1 to a recording medium sending mechanism 44for elongated hologram recording medium h₁ which will be described laterin correspondence with output timing of element hologram image data DSto carry out operation control thereof to control sending operation ofthe hologram recording medium h₁.

In such object optical system 30B, object light L2 in point light sourcestate incident from the incident optical system 30A in a divided stateis magnified by the first cylindrical lens 35, and is incident on thecollimator lens 36 so that parallel light is provided. Further, in theobject optical system 30B, object light L2 incident on the transmissiontype liquid crystal indicator 39 through the collimator lens 36 isimage-modulated in accordance with element hologram image displayed onthis transmission type liquid crystal indicator 39, and is incident onthe second cylindrical lens 38 through the projection lens 37. Further,the object optical system 30B allows image-modulated object light L2 tobe incident on hologram recording medium h₁ of the exposure recordingunit P1 for a time period during which the shutter mechanism 32 iscaused to undergo opening operation to carry out exposure recordingthereof in correspondence with element hologram image. At this time,exposure recording is carried out by using direct light from the secondcylindrical lens 38 without diffusing object light L2. The detailthereof will be described later.

The reference optical system 30C has the configuration in which acylindrical lens 40, a collimator lens 41 and a reflection mirror 42 aresuccessively arranged in order from the input side thereof along theoptical axis.

The cylindrical lens 40 has the configuration in which convex lens andpin hole are combined similarly to the first cylindrical lens 35 in theabove-described object optical system 30B, and magnifies, inone-dimensional direction, reference light L3 reflected and divided bythe half mirror 33 in correspondence with a predetermined width, i.e.,display surface width of the transmission type liquid crystal indicator39 specifically.

The collimator lens 41 changes reference light L3 magnified by thecylindrical lens 40 into parallel light.

The reflection mirror 42 reflects reference light L3 to conductreflected light toward backward direction of the hologram recordingmedium h₁ of the exposure recording unit P1 to allow it to be incidentthereupon.

As described above, such first optical system 30 is constituted so thatoptical path lengths of the object optical system 30B which is anoptical system through which object light L2 divided by the half mirror33 is passed and the reference optical system 30C which is an opticalsystem through which reference light L3 is passed are caused to besubstantially the same. Accordingly, the first optical system 30produces holographic stereogram in which coherence between object lightL2 and reference light L3 is improved so that more clear reproductionimage can be obtained.

Further, at the first optical system 30, there is provided, as occasiondemands, an interference fringes detecting unit 43 for stopping exposurerecording of hologram recording medium h₁ in the case where there takesplace the possibility that holographic stereogram of satisfactory stateis not produced by vibration, etc.

The interference fringes detecting unit 43 detects the state ofinterference fringes formed by object light L2 and reference light L3which are respectively incident on the hologram recording medium h₁through the above-described respective optical systems. The interferencefringe detecting unit 43 is constituted by, e.g., CCD (Charge CoupledDevice) camera, and detects fluctuation state of interference fringesformed in the detection area different from the exposure formation areaof holographic stereogram at the hologram recording medium h₁ bywavelength order of laser beam L1 emitted from the laser light source31.

When the interference fringes detecting unit 43 detects, within thedetection area, appearance of interference fringes of fluctuation statemore than a predetermined value, it provides detection signal to thecontrol computer 13. The control computer 13 allows the shuttermechanism 32 to be inoperative state on the basis of this detectionsignal. Accordingly, in the hologram recording medium h₁, becauseincidence of object light L2 and reference light L3 is interrupted,production of holographic stereogram is stopped. Moreover, wheninterference fringes formed in the detection area are in fluctuationstate within a predetermined value, the interference fringes detectingunit 43 stops delivery of detection signal with respect to the controlcomputer 13. The control computer 13 allows the shutter mechanism 32 tobe in operative state by this operation to cause object light L2 andreference light L3 to be incident on the hologram recording medium h₁ sothat holographic stereogram can be produced.

Moreover, the holographic stereogram producing unit 20 including thefirst optical system 30 includes a recording medium sending mechanism 44for carrying out intermittent sending of the hologram recording mediumh₁ by one element hologram in a direction indicated by arrow a in FIG.9B.

The recording medium sending mechanism 44 intermittently carries outtraveling drive of hologram recording medium h₁ on the basis of controlsignal C1 provided from the control computer 13. In addition, theholographic stereogram producing unit 20 operates the above-describedshutter mechanism 32 on the basis of control signal C1 provided from thecontrol computer 13 in a manner interlocking with the operation of thisrecording medium sending mechanism 44 to release the optical path oflaser beam L1.

The holographic stereogram producing unit 20 carries out traveling driveof the hologram recording medium h₁ along the traveling path by quantitycorresponding to one element hologram because of that control signal C1corresponding to one element hologram is provided from the controlcomputer 13 in the control unit 12 to the recording medium sendingmechanism 44 every completion of exposure recording corresponding to oneelement image to stop the hologram recording medium h₁ in the statewhere unexposed portion is caused to be in correspondence with theexposure recording unit P1. It is to be noted that the holographicstereogram producing unit 20 is constituted so that vibration producedin the hologram recording medium h₁ followed by traveling operation ofthe hologram recording medium h₁ is rapidly stopped. In this example, asdescribed above, the hologram recording medium h₁ consists of elongatedphotosensitive film, and is wound on delivery roll rotatably providedwithin the film cartridge in which, e.g., the entirety is held in lightshielding state although not shown. When this film cartridge is loadedinto the holographic stereogram producing unit 20, the hologramrecording medium h₁ is drawn out toward the inside of the holographicstereogram producing unit 20, and is caused to undergo traveling driveat the traveling path by the recording medium sending mechanism 44.

The holographic stereogram producing unit 20 allows object light L2which has been image-modulated from surface and back thereof withrespect to hologram recording medium h₁ because of that the shuttermechanism 32 is caused to undergo opening operation in this state andreference light L3 to be incident on the hologram recording medium h₁ atthe exposure recording unit P1 to carry out exposure recording ofinterference fringes corresponding to element hologram image. Theholographic stereogram producing unit 20 is adapted so that whenexposure recording of one element image is completed, control signal C1is provided from the control computer 13 at the control unit 12 to therecording medium sending mechanism 44 to allow the hologram recordingmedium h₁ to quickly undergo traveling drive by a predetermined quantityto stop it.

The holographic stereogram producing unit 20 carries out such operationin succession below to successively carry out exposure recording ofplural holographic stereogram images on elongated hologram recordingmedium h₁ to produce holographic stereograms.

After exposure recording, a predetermined fixing processing isimplemented to the holographic stereograms thus produced. To simplyspeak, at the fixing processing, ultraviolet ray LB having power ofabout 1000 mJ/cm² is irradiated to complete polymerization of monomers Min matrix polymer to increase refractive index modulation factor of thatphoto-polymer layer by heat treatment at about 120° C.

The holographic stereograms are cut out by cutter (not shown) everyholographic stereogram image after fixing processing, and theholographic stereograms thus cut are used as the original H₁.

On the basis of the original H₁ produced in a manner as described above,at the hologram duplicating unit 50 including the second optical system60 and the third optical system 70, edge lit hologram H₃ is finallyduplicated through intermediate hologram H₂.

First, at the second optical system 60, as shown in FIG. 10,intermediate hologram H₂ is produced from the original H₁. Namely,reproduction light is irradiated onto the original H₁, and itsdiffracted light is irradiated as object light L5 onto an unrecordedrecording medium h₂ for hologram placed at the position where imagerecorded on the original H₁ is formed. Reference light L6 is irradiatedonto the hologram recording medium h₂ from the surface of the sideopposite to the surface where object light L5 is irradiated, andinterference fringes of the object light L5 and the reference light L6are recorded onto the hologram recording medium h₂. This is used atthird optical system 70 which will be described later as intermediatehologram H₂. Here, the hologram recording medium h₂ has the same qualityas the hologram recording medium 3.

The configuration of the second optical system 60 is shown in FIG. 11.An incident optical system 60A includes a laser light source 61 foremitting laser beam L4, and a half mirror 62 for dividing this laserbeam L4 into object light L5 and reference light L6.

The laser light source 61 is a laser unit, such as, for example,semiconductor excitation YAG laser unit, water-cooled argon ion laserunit or water-cooled krypton laser unit, etc. which emits coherent laserbeam L4 of the single wavelength, etc.

Transmission to the succeeding stage of this laser beam L4 is controlledby shutter mechanism (not shown). Namely, the shutter mechanism iscaused to undergo opening/closing operation by control signal C2outputted from the control computer 13 to allow laser beam L4 to beincident on the original H₁ and hologram recording medium h₂ through theoptical system of the succeeding stage, or to interrupt incidence on theoriginal H₁ and the hologram recording medium h₂ of laser beam L4.

The half mirror 62 divides incident laser beam L4 into transmitted lightand reflected light. With respect to laser beam L4, transmitted light isused as the above-described reference light L6, whereas reflected lightis used as object light L5. The object light L5 and the reference lightL6 are respectively incident on an object optical system 60B and areference optical system 60C provided at the succeeding stages.

The object optical system 60B has the configuration in which opticalparts such as a cylindrical lens 63, a collimator lens 64, and areflection mirror 65, etc. are arranged in order from the input sidethereof along the optical path.

The cylindrical lens 63 has the configuration in which convex lens andpin hole are combined, and magnifies object light L5 which is reflectedlight reflected by the half mirror 62 in one-dimensional direction.

The collimator lens 64 changes object light L5 magnified by thecylindrical lens 63 into parallel light.

The reflection mirror 65 reflects object light L5 to conduct thereflected light toward backward portion of the original H₁ produced atthe first optical system 30 to allow it to be incident. Thus, imagerecorded on the original H₁ is reproduced at the position of thehologram recording medium h₂.

The reference optical system 60C has the configuration in which opticalparts such as a reflection mirror 66, a cylindrical lens 67, and acollimator lens 68, etc. are arranged in order from the input sidethereof along the optical axis.

The reflection mirror 66 totally reflects reference light L6 transmittedthrough the half mirror 62. Reference light L6 totally reflected by thisreflection mirror 66 is provided to the cylindrical lens 67.

The cylindrical lens 67 has the configuration in which convex lens andpin hole are combined, and magnifies reference light L2 totallyreflected by the reflection mirror 66 in one-dimensional direction.

The collimator lens 68 changes reference light L6 magnified by thecylindrical lens 67 into parallel light to conduct the parallel light tothe backward portion of the hologram recording medium h₂ to allow it tobe incident.

As described above, such second optical system 60 is constituted so thatoptical path lengths of the object optical system 60B which is anoptical system through which object light L5 divided by the half mirror62 is passed and the reference optical system 60C which is an opticalsystem through which reference light L6 is passed are caused to besubstantially the same. Accordingly, the second optical system 60produces hologram in which coherence between object light L5 andreference light L6 is improved so that more clear reproduction image canbe obtained.

By the configuration as described above, the second optical system 60allows object light L5 and reference light L6 to interfere with eachother at the inside of the hologram recording medium h₂ to causeinterference fringes produced by interference to undergo exposurerecording to produce intermediate hologram H₂. After exposure recording,similarly to the case of the first optical system 30, a predeterminedfixing processing is implemented. The intermediate hologram H₂ producedin this way is used at the third optical system 70.

Then, the third optical system 70 will be described. At the thirdoptical system 70, as shown in FIG. 12, edge lit hologram H₃ is producedfrom intermediate hologram H₂. Namely, reproduction light is irradiatedonto the intermediate hologram H₂, and its diffracted light isirradiated, as object light L8, through an one-dimensional diffusionplate 76, onto recording medium h₃ for hologram placed at the distancewhere image recorded on the intermediate hologram H₂ is formed. A lightintroduction block BL consisting of transparent optical material such asglass or plastic, etc. of a suitable thickness is stuck onto thehologram recording medium h₃, and reference light L9 is irradiated fromthe side surface of the surface where object light L8 is irradiated.Interference fringes of the object light L8 and the reference light L9are recorded onto the hologram recording medium h₃. Here, the hologramrecording medium h₃ has the same quality as the hologram recordingmedium 3. Moreover, although not shown, the light introduction block BLis stuck onto the hologram recording medium h₃ through adhesive layer,e.g., index matching liquid, etc. having a refractive index such thatthe hologram recording medium h₃ and the light introduction block BL arenot caused to undergo total reflection.

Here, the holographic stereogram maintains angle of visibility inparallax direction because of that plural element holograms are arrangedin one direction, but sacrifices parallax with respect to the directionperpendicular thereto. Namely, in the holographic stereogram, sufficientangle of visibility can be maintained in parallax direction, but angleof visibility cannot be maintained in a perpendicular direction. Forthis reason, it is necessary to use an one-dimensional diffusion platefor the object optical system to compensate angle of visibility in thatdirection.

However, when one-dimensional diffusion plate is used at the firstoptical system 30 or the second optical system 60, recording medium hfor hologram which is photosensitive material must be enlarged in orderto record diffused diffracted light in exposure of the next stage. As aresult, it is difficult that the optical system becomes compact. Inaddition, rigorous precision is required for plane characteristic orangle with respect to optical axis of photosensitive material, etc.Particularly, when one-dimensional diffusion plate is used at the firstoptical system 30, brightness is lowered by diffusion of object light,and degradation in image quality thereafter becomes conspicuous.

In view of the above, in the hologram duplicating apparatus 10 in thisembodiment, the above-described one-dimensional diffusion plate 76 isdisposed as shown in FIG. 12 immediately before recording medium h₃ forhologram at the third optical system 70 without using theone-dimensional diffusion plate at the first optical system 30 tomaintain angle of visibility in a direction perpendicular to parallaxdirection.

The configuration of the third optical system 70 is shown in FIG. 13. Anincident optical system 70A includes a laser light source 71 foremitting laser beam L7, and a half mirror 72 for dividing this laserlight L7 into object light L8 and reference light L9.

The laser light source 71 is a laser unit, e.g., semiconductorexcitation YAG laser unit, water-cooled argon ion laser unit orwater-cooled krypton unit which emits coherent laser beam L7 of singlewavelength, etc.

Transmission to the succeeding stage of this laser beam L7 is controlledby shutter mechanism (not shown). Namely, the shutter mechanism iscaused to undergo opening/closing operation by control signal C2outputted from the control computer 13 to allow laser beam L7 to beincident on intermediate hologram H₂ and hologram recording medium h₃through the optical system of the succeeding stage, or to interruptincidence on intermediate hologram H₂ and hologram recording medium h₃of laser beam L7.

The half mirror 72 divides incident laser beam L7 into transmitted lightand reflected light. With respect to the laser beam L7, transmittedlight is used as the above-described object light L8, whereas reflectedlight is used as reference light L9. The object light L8 and thereference light L9 are respectively incident on an object optical system70B and a reference optical system 70C provided at the succeedingstages.

The object optical system 70B has the configuration in which opticalparts such as a reflection mirror 73, a cylindrical lens 74, acollimator lens 75, and one-dimensional diffusion plate 76, etc. arearranged in order from the input side thereof along the optical axis.

The reflection mirror 73 totally reflects object light L8 transmittedthrough the half mirror 72. The object light L8 totally reflected bythis reflection mirror 73 is provided to the cylindrical lens 74.

The cylindrical lens 74 has the configuration in which convex lens andpin hole are combined, and magnifies object light L8 totally reflectedby the reflection mirror 73 in one-dimensional direction.

The collimator lens 75 changes object light L1 magnified by thecylindrical lens 74 into parallel light to irradiate the parallel lightonto intermediate hologram H₂, and its diffracted light is incident onthe one-dimensional diffusion plate 76.

The one-dimensional diffusion plate 76 diffuses object light L1 inone-dimensional direction as described above to allow the object lightL1 to be incident on hologram recording medium h₃.

The reference optical system 70C has the configuration in which acylindrical lens 77, a collimator lens 78 and a reflection mirror 79 arearranged in order from the input side thereof along the optical axis.

The cylindrical lens 77 has the configuration in which convex lens andpin hole are combined similarly to the cylindrical lens 74 in theabove-described object optical system 70B, and magnifies reference lightL9 reflected and divided by the half mirror 72 in one-dimensionaldirection in correspondence with a predetermined width.

The collimator lens 78 changes reference light L9 magnified by thecylindrical lens 77 into parallel light.

The reflection mirror 79 reflects reference light L9 to conduct thereflected light to the side surface of the light introduction block BLof the hologram recording medium h₃ to allow it to be incident. Thereference light L9 incident on the side surface of the lightintroduction block BL is incident on the backward portion of thehologram recording medium h₃.

As described above, such third optical system 70 is constituted so thatoptical path lengths of the object optical system 70B which is anoptical system through which object light L8 divided by the half mirror72 is passed and the reference optical system 70C which is an opticalsystem through which reference light L9 is passed are caused to besubstantially the same. Accordingly, the third optical system 70produces edge lit hologram H₃ in which coherence between object light L8and reference light L9 is improved so that more clear reproduction imagecan be obtained.

By the configuration as described above, the third optical system 70allows object light L8 and reference light L9 to interfere with eachother at the inside of hologram recording medium h₃ to causeinterference fringes produced by interference to undergo exposurerecording to produce edge lit hologram H₃. After exposure recording,similarly to the case of the first optical system 30, a predeterminedfixing processing is implemented. In addition, by repeating theoperation in the above-described third optical system 70, it is possibleto extensively duplicate an arbitrary number of edge lit holograms H₃ onthe basis of the original As stated above, the hologram duplicatingapparatus 10 in this embodiment can be constituted by makingimprovements on the basis of existing holographic stereogram producingsystem, and can duplicate holograms in which brightness is maintainedand angle of visibility is maintained.

Particularly, edge lit hologram H₃ duplicated by this hologramduplicating apparatus 10 has merits such that since transmitted lightwhich does not contribute to reproduction is confined within lightintroduction block BL by total reflection so that it does not leaktoward the outside, guide wave is efficiently carried out so that brightimage is reproduced, and since angle of reproduction is great, image isdifficult to be reproduced by light entered from the outside of thelight introduction block BL except for reproduction light.

Moreover, the edge lit type is employed, thereby making it possible toinclude the light source within the light introduction block BL. Thus,it is also possible to maintain brightness irrespective of illuminationenvironment.

It is to be noted that this invention is not limited only to theabove-described embodiment, but it is a matter of course that variouschanges can be made within the scope which does not depart from the gistof this invention.

While, e.g., edge lit holograms are duplicated from holographicstereogram serving as an original in the above-described embodiment,this invention is not limited to this implementation, but it issufficient to duplicate ordinary holograms.

Further, while it has been described that holographic stereogramproducing unit 20 and hologram duplicating unit 50 are provided insingle hologram duplicating apparatus 10, it is sufficient that bothunits are separate units, and holograms may be duplicated using thealready produced holographic stereogram as the original.

Further, the second optical system 60 and the third optical system 70included in the hologram duplicating unit 50 may be constituted asseparate units. Furthermore, the second optical system 60 and the thirdoptical system 70 may also have the configuration in which both systemsshare a partial optical system such as reproduction optical system forreproducing image or exposure recording optical system for carrying outexposure recording of reproduced image to first produce intermediatehologram H₂ thereafter to produce edge lit hologram H₃.

In addition, there may be employed a configuration to produceintermediate hologram H₂ by separate unit to produce edge lit hologramH₃ by using this intermediate hologram H₂.

INDUSTRIAL APPLICABILITY

By using this invention as described above, it becomes possible toduplicate or produce a large quantity of holograms or edge lit hologramswithout lowering image quality in the state where holographic stereogramis used as the original.

1. A hologram duplicating apparatus adapted for duplicating a hologram in which a holographic stereogram is used as an original, the hologram duplicating apparatus comprising: a first optical system for allowing a first object light, which has been image-modulated on the basis of respective element images of a parallax image sequence to be incident on a first surface of a first hologram recording medium without diffusion, and for allowing a first reference light having coherence with the first object light to be incident on an opposite surface of the first hologram recording medium so as to successively carry out exposure recording of interference fringes produced by the first object light and the first reference light on the first hologram recording medium as element holograms, thereby producing the original; a second optical system for allowing a diffracted light obtained by irradiating a first reproduction light onto the original for reproducing the original to be incident as a second object light on a first surface of a second hologram recording medium disposed with a predetermined distance from the original, and for allowing a second reference light having coherence with the second object light to be incident on an opposite surface of the second hologram recording medium to carry out exposure recording of interference fringes produced by the second object light and the second reference light on the second hologram recording medium as holograms, thereby producing an intermediate hologram; and a third optical system in which a one-dimensional diffusion plate for diffusing incident light in a one-dimensional direction is disposed at a first surface of a third hologram recording medium disposed with a predetermined distance from the intermediate hologram produced by the second optical system in such a manner that the principal surface thereof is in contact therewith, the third optical system for allowing a diffracted light obtained by irradiating a second reproduction light onto the intermediate hologram for reproducing the intermediate hologram to be incident on the first surface of the third hologram recording medium as a third object light through the one-dimensional diffusion plate, and for allowing a third reference light having coherence with the third object light to be incident on an opposite other surface of the third hologram recording medium to carry out exposure recording of interference fringes produced by the third object light and the third reference on the third hologram recording medium as holograms, thereby producing a duplicated hologram.
 2. The hologram duplicating apparatus as set forth in claim 1, wherein a light introduction block consisting of transparent optical material is attached on the opposite surface of the third hologram recording medium where the third reference light is incident.
 3. A hologram duplicating method of duplicating hologram in which a holographic stereogram is used as an original, the hologram duplicating method including: a first exposure step of allowing a first object light, which has been image-modulated on the basis of respective element images of parallax image sequence to be incident on a first surface of a first hologram recording medium without diffusion, and of allowing a first reference light having coherence with the first object light to be incident on an opposite surface of the first hologram recording medium so as to successively carry out exposure recording of interference fringes produced by the first object light and the first reference light on the first hologram recording medium as element holograms, thereby producing the original; a second exposure step of allowing a diffracted light obtained by irradiating a first reproduction light onto the original for reproducing the original to be incident as a second object light on a first surface of a second hologram recording medium disposed with a predetermined distance from the original, and of allowing a second reference light having coherence with the second object light to be incident on an opposite surface of the second hologram recording medium to carry out exposure recording of interference fringes produced by the second object light and the second reference light on the second hologram recording medium as hologram, thereby producing an intermediate hologram; and a third exposure step in which a one-dimensional diffusion plate for diffusing incident light in one-dimensional direction is disposed at a first surface of a third hologram recording medium disposed with a predetermined distance from the intermediate hologram produced at the second exposure step in such a manner that the principal surface thereof is in contact therewith, the third exposure step of allowing a diffracted light obtained by irradiating a second reproduction light onto the intermediate hologram for reproducing the intermediate hologram to be incident on the first surface of the third hologram recording medium as a third object light through the one-dimensional diffusion plate, and of allowing a third reference light having coherence with the third object light to be incident on an opposite other surface of the third hologram recording medium to carry out exposure recording of interference fringes produced by the third object light and the third reference light on the third hologram recording medium as holograms, thereby producing a duplicated hologram.
 4. The hologram duplicating method as set forth in claim 3, wherein a light introduction block consisting of transparent optical material is attached on the opposite surface of the third hologram recording medium where the third reference light is incident.
 5. A hologram producing apparatus adapted for producing a hologram using an original holographic stereogram having the configuration in which plural element holograms are successively arranged along a parallax direction, the hologram producing apparatus comprising: intermediate hologram producing means for reproducing an image of the original holographic stereogram to carry out exposure recording of a reproduced image of the original holographic stereogram on a first hologram recording medium to thereby produce an intermediate hologram; and hologram producing means for reproducing an image of the intermediate hologram to carry out exposure recording of a reproduced image of the intermediate hologram on a second hologram recording medium to thereby produce the hologram, wherein the hologram producing means comprises, at the surface of the second hologram recording medium, diffusing means for diffusing the reproduced image of the intermediate hologram in a direction corresponding to a direction perpendicular to the parallax direction at the original holographic stereogram.
 6. The hologram producing apparatus as set forth in claim 5, wherein the intermediate hologram producing means and the hologram producing means share a reproduction optical system for reproducing the image of the original holographic stereogram and the image of the intermediate hologram and an exposure recording optical system for carrying out exposure recording of the reproduced image of the original holographic stereogram and the reproduced image of the intermediate hologram.
 7. A hologram producing apparatus adapted for reproducing an image using an original holographic stereogram having the configuration in which plural element holograms are successively arranged along a parallax direction to produce a hologram by using an intermediate hologram produced by carrying out exposure recording of a reproduced image on a first hologram recording medium, the hologram producing apparatus comprising: hologram producing means for reproducing an image of the intermediate hologram to carry out exposure recording of the reproduced image of the intermediate hologram on a second hologram recording medium to thereby produce the hologram, wherein the hologram producing means comprises, at a surface of the second hologram recording medium, diffusing means for diffusing the reproduced image of the intermediate hologram in a direction corresponding to a direction perpendicular to the parallax direction at a surface of the original.
 8. A hologram producing method of producing a hologram using an original holographic stereogram having the configuration in which plural element holograms are successively arranged along a parallax direction, the hologram producing method including: an intermediate hologram producing step of reproducing an image of the original holographic stereogram to carry out exposure recording of the reproduced image of the original holographic stereogram on a first hologram recording medium to thereby produce an intermediate hologram; and a hologram producing step of reproducing an image of the intermediate hologram to carry out exposure recording of the reproduced image of the intermediate hologram on a second hologram recording medium to thereby produce the hologram, wherein, at the hologram producing step, the image of the intermediate hologram that is reproduced to produce the hologram is diffused by diffusing means disposed on a surface of the second hologram recording medium in a direction corresponding to a direction perpendicular to the parallax direction at a surface of the original holographic stereogram, wherein, at the intermediate hologram producing step and the hologram producing step, a reproduction optical system for reproducing the image of the original holographic stereogram and the image of the intermediate hologram and an exposure recording optical system for carrying out exposure recording of the reproduced image of the original holographic stereogram and the reproduced image of the intermediate hologram are shared. 